EP 0 984 286 A1 discloses a sealing system whereby the gap between a housing and a shaft is sealed with a sealing ring. In addition to the sealing ring, a multipole ring is placed on the shaft. The multipole ring cooperates with a measuring sensor disposed on the machine housing. By means of the measuring sensor, it is possible to measure, for example, the rotation speed of the shaft. The quantities measured are transmitted through an electric cable to a control unit and/or a display or the like.
DE 43 12 424 C2 also describes the possibility of mounting a sealing ring and a rotation speed transmitter device for the purpose of sealing a shaft passage in an external front wall of a housing.
Moreover, the DE 101 49 642.7 describes a number of embodiments of sealing rings in connection with sensor housings.
The common feature of all prior-art designs is that the measuring sensors, namely the sensing elements, must be supplied with current from the outside and that the quantities measured also must be transmitted via a cable to a display and/or control unit. The cable or cables require a plug connector which reduces the signal accuracy. Moreover, the cables require mounting space and good accessibility, particularly in the event that repairs are needed. Accessibility usually requires additional mounting space.